Near infrared imaging

ABSTRACT

An endoscope or wand device comprising transmitting members, in which the transmitting members comprise a coating that transmits between about 95% and about 99.5% of energy at a wavelength within the infra red spectrum.

RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser.No. 60/771,288 filed on Feb. 7, 2006, and entitled “Endoscopes andWands”, U.S. Provisional Application Ser. No. 60/793,979 filed on Apr.20, 2006 and entitled “Endoscopes and wands”, and U.S. ProvisionalApplication Ser. No. 60/828,627 filed on Oct. 6, 2006 and entitled“Endoscopes and Wands”. Each of these applications is herebyincorporated by reference in its entirety. Each of these areincorporated by reference in their entirety.

TECHNICAL FIELD

This application relates to endoscopes and similar devices.

BACKGROUND OF THE INVENTION

An endoscope or wand viewing apparatus is usually configured in a waythat is well suited for illumination and imaging in visible light.

In this background section endoscopes and wand like devices shall bedescribed in terms of their internal working components. In the secondportion of the background section the shortcomings of these predicatedevices shall be described with respect to their use for laser inducedfluorescence imaging.

An endoscope is an opto-mechanical imaging device characterized by thefollowing: an objective lens assembly containing an optional deviatingprism assembly, a relay system forming a plurality of intermediateimages for the case of a rigid endoscope, an ocular, a camera systemcontaining multiple detectors with a prism assembly directing sectionsof the electromagnetic spectrum to dedicated sensors, or in the case ofchip-on-a-stick endoscope where there are no intermediate images; anobjective lens assembly coupled directly to the camera detector which isembedded in the distal most portion of the device. In either case theoptical elements are contained in an inner most tube member which issurrounded by other tube members which may include fiber optics forillumination in the annulus formed by two or more of the tubes and maycontain other tubes for the passage of instruments and or irrigation.

An objective lens assembly in the distal most portion of the deviceforms a real image of the scene coincident with the plane of thedetector in the case of a chip-on-a-stick endoscope or intraoral camera,or distal most plane of a relay system that is contained within theshaft portion of the endoscope.

In an endoscope with a relay system (the second case above), there are 2basic forms of relays, those of lenses and those using coherent imagingfibers.

In both examples the role of the relay is to reform the image producedby the objective lens through the length of the shaft by producingintermediate images in the case of a rigid endoscope to a new positionwhere the ocular, in the case of a visual endoscope or camera lens groupin the case of a digital or electronic imaging device, may then reformthe image originally produced by the objective lens group for the eye orto a camera detector.

The shaft portions of all endoscopes are made to facilitate theinsertion of the device into a body cavity or body lumen, that is to saydiameter is the dimension being minimized. In the case of a body cavityinsertion, the shaft is often rigid and comprised of thin walledstainless steel tubes. This tube within tube construction allows for aninnermost tube to contain the optical train and then surrounding tubescan contain fiber optics to transmit illumination to the scene in theform of an annulus. Additional tubes can be contained within theassembly for the introduction of surgical instruments for variouspurposes.

For the case of an endoscope that utilizes coherent imaging fibers forthe relay system the functional concept being optimized in the device isflexibility, and to some degree what is being compromised is resolution,particularly when the diameter of the tip is small. However, largediameter flexible endoscopes often use detectors directly behind theobjective lens assembly and are therefore considered “chip-on-a-stick”configurations. These flexible endoscopes often have internal channels,instrument and irrigation channels, to pass forceps, etc. and haveinternal guide wires and steering mechanisms at the tip controlled bylevers at the proximal end of the device.

There is a class of smaller diameter endoscopes utilizing coherentimaging fibers as relays whose shafts have a limited amount offlexibility, and these devices are commonly called semi-flexible. Oftenconfigured with a working channel, called a forceps channel, used forinstruments and are often used in Urology.

Whether rigid, flexible, or semi-flexible, endoscopes have a proximaleyepiece section for viewing and or coupling to a camera system. Aneyepiece is not present on chip-on-a-stick endoscopes or intraoralcameras, often called dental cameras, as the camera is imbedded into thedistal portion of the device.

Where eyepieces are used, manufacturers have almost universally adopteda nominal 32 mm eye cup for blocking room light from the physician'sview, and this eye cup serves to support the coupling mechanism to thecamera. There are some commercial applications of directly coupling thecamera and optical assemblies included in the shaft mechanism and orcoupling mechanism but this has not found wide acceptance, except inOrthopedics for Arthroscopy. The fear among users has been that if theelectronics of the camera fail for some reason then the doctor is leftwith no means to view within the patient, hence the continuing presenceof endoscopes with eyepieces.

The class of endoscopes not utilizing eyepieces is commonly calledchip-on-a-stick. The intraoral dental camera shares the lack of eyepieceor ocular, as well. Both instruments send a video signal to a monitor orcomputer for viewing.

Endoscopes are most commonly fixed focus imaging devices. There is abroad distance from the tip of the device to the subject that is infocus due to the relatively small aperture of the optical system. Asmall aperture allows only a small amount of light to be imagined forany point in the scene. Should focusing be required it is accomplishedby repositioning the optics in the camera module proximal to theendoscope, or in some cases the detector itself is moved.

Such low levels of return signal in the visible spectrum requireendoscopes to have large light sources such as xenon, halogen, and metalhalide.

In the case of an endoscope, commonly called a chip-on-a-stick whichcontain a distal most detector (CCD, CMOS, or other sensor), the changein image plane position for a near object of interest versus a farobject of interest is usually ameliorated by installing a very smallaperture in the objective lens assembly to increase depth of field atthe expense of a bright field or higher potential resolution.

This is a distinction between endoscopes and chip-on-a-stick endoscopesregarding focus. Endoscopes with proximal cameras do provide a means forfocus even if they themselves are fixed focus. Chip-on-a-stickendoscopes usually do not provide a focus means. However, large diameterflexible endoscopes used in gastroenterology do often have moveabledetectors or lenses providing focus.

For smaller chip-on-a-stick endoscopes, all of the optical elements inthe objective lens assembly are optimized for the small aperture whichallows great depth of field. It is not the case that the aperture couldbe removed for increased brightness. The advantage is that no motion(focus) is required and when provided with powerful illumination systemsin the visible light the overall system can perform well given theconstraint of illumination.

A focus means becomes an area of distinction between a chip-on-a-stickendoscope and a wand imaging device, referred to as an intraoral ordental camera, as well. Both chip-on-a-stick endoscope and a wandimaging devices contain the detector plane in the distal or forwardportion of the device directly behind the objective lens assembly. Theintraoral or dental camera is often required to be used in stand offmode, a distance that is greater than endoscopy requires. Thedistinction results from the use; endoscopy is done in closed surgicalor diagnostic sites, the intraoral devices are used external to the bodyor inserted in natural cavities such as the mouth. In such stand offmodes, not the mouth but full face views, great amounts of illuminationwould be required to satisfy the large change in s and s′ (the opticalpath length on either side of the objective lens) in the intraoral ordental camera where to be fixed focus. Therefore, intraoral or wand likedental cameras frequently contain a means to move the detector plane, orfocus the device. Using a faster F number, with inherently less depth offield but higher sensitivity, and by moving the detector plane a lowerpowered illumination system is required. This allows a wand with near IRcapabilities to accommodate large changes in distances to the object ofinterest, thereby allowing a faster optical system to be designed, acharacteristic that requires variable focus, but provides higherinherent resolution, and more conservative illumination sources.

Endoscopes and wands are generally designed to visualize in the visiblespectrum. However, fluorescent dyes, such as indocyanine green (ICG)(Akorn, Inc., Buffalo Grove, Ill.) are commonly being used to imageanatomy in the infra red spectrum. Use of ICG is described in, forexample, U.S. Pat. No. 6,915,154, which is incorporated herein byreference in its entirety. Once excited, ICG emits in the infra redspectrum at about 825 to about 835 nm. FIG. 1 shows the excitation andemission spectrum of the ICG composition sold by Akorn, Inc. There istherefore a need for endoscope and wand devices that are capable ofimaging and visualizing in the infrared spectrum.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the excitation and emission spectrum of the ICG compositionsold by Akorn, Inc.

FIG. 2 illustrates an endoscopic system.

FIG. 3 illustrates an endoscope.

FIG. 4 illustrates certain endoscope components. The left side of FIG. 4illustrates multiple examples of objective assemblies, only one of whichwould commonly be used in any particular endoscope. The middle of FIG. 4illustrates multiple examples of relays, of which only one wouldcommonly be used in a particular endoscope. The right hand side of FIG.4 illustrates a 2 channel prism or a 4 channel prism (the bottom twodrawings showing the same 4 channel prism from different views).Commonly only one of a 2 or a 4 channel prism would be used in anyparticular endoscope.

FIG. 5 illustrates deviating prisms.

FIG. 6 illustrates representative scans of prior art coatings.

FIGS. 7 and 8 each illustrate details of coatings.

FIG. 9 illustrates a 2 chip prism assembly. Angles shown are merelyexemplary.

FIG. 10 illustrates a 4 chip prism assembly. Angles shown are merelyexemplary.

FIG. 11 illustrates a light source.

FIG. 12 illustrates a second embodiment of the light source.

MODES FOR CARRYING OUT THE INVENTION AND INDUSTRIAL APPLICABILITY

The invention provides endoscope and wand devices and systems forimaging in the infrared spectrum, and preferably in multiple spectrumsat least one of which is infrared. Imaging of fluorescent emissions inthe infrared spectrum is particularly difficult because the nearinfrared light emitted by a fluorescent dye may be an order of magnitudeor more lower than the visible light reflected or emitted by a subject.A “device” is any hand-held instrument designed to view or imageanatomy, either inside or outside a patient's body.

In certain embodiments, the invention provides an endoscope or wanddevice having relay optics such as glasses. The transmitting membershave a coating that transmits between about 95% and about 99.5% ofenergy at a wavelength within the infra red spectrum.

In some embodiments, the invention provides a prism assembly forseparating visible light from infra red light. The prism assemblycontains at least one channel configured to receive and transmit lightin the visible spectrum and at least a second channel configured toreceive and transmit light in the infra red spectrum.

Hereinafter, aspects in accordance with various embodiments of theinvention will be described. As used herein, any term in the singularmay be interpreted to be in the plural, and alternatively, any term inthe plural may be interpreted to be in the singular.

Definitions

“Approximately”, “substantially” and “about” each mean within 10%,preferably within 6%, more preferably within 4% even more preferablywithin 2%, and most preferably within 0.5% of the stated number or range

“Computer” as used herein, refers to a conventional computer asunderstood by the skilled artisan. For example, a computer generallyincludes a central processing unit that may be implemented with aconventional microprocessor, a random access memory (RAM) for temporarystorage of information, and a read only memory (ROM) for permanentstorage of information. A memory controller is provided for controllingRAM. A bus interconnects the components of the computer system. A buscontroller is provided for controlling the bus. An interrupt controlleris used for receiving and processing various interrupt signals from thesystem components. Mass storage may be provided by diskette, CD ROM,DVD, USB stick, or hard drive. Data and software may be exchanged withcomputer system via removable media such as the diskette, USB stick, orCD ROM. A CD ROM or DVD drive is connected to the bus by the controller.The hard disk is part of a fixed disk drive that is connected to the busby a controller. User input to the computer may be provided by a numberof devices. For example, a keyboard and mouse may be connected to thebus by a controller. An audio transducer that might act as both amicrophone and a speaker may be connected to the bus by an audiocontroller. It will be obvious to those reasonably skilled in the artthat other input devices, such as a pen and/or tablet may be connectedto the bus and an appropriate controller and software, as required. Avisual display can be generated by a video controller that controls avideo display. Preferably, the computer further includes a networkinterface that allows the system to be interconnected to a local areanetwork (LAN) or a wide area network (WAN). Operation of the computer isgenerally controlled and coordinated by operating system software, suchas the Solaris operating system, commercially available from SunMicrosystems, the UNIX® operating system, commercially available fromThe Open Group, Cambridge, Mass., the OS-X® operating system,commercially available from Apple, Inc., Cupertino Calif. or the WindowsXP® or VISTA® operating system, commercially available from MicrosoftCorp., Redmond, Wash., or the Linux open source operating systemavailable from multiple sources. The operating system controlsallocation of system resources and performs tasks such as processingscheduling, memory management, networking, and I/O services, amongthings. In particular, an operating system resident in system memory andrunning on the CPU coordinates the operation of the other elements ofcomputer. “Subject” as used herein, refers to any animal. The animal maybe a mammal. Examples of suitable mammals include, but are not limitedto, humans, non-human primates, dogs, cats, sheep, cows, pigs, horses,mice, rats, rabbits, and guinea pigs.

As used herein, “wavelength of interest” refers to light in both thevisible and infra red spectrum. In some embodiments, it refers to lightin only the infra red spectrum. In some embodiments, it includes lightat the wavelength at which ICG fluoresces. In some embodiments, itincludes light between about 825 and about 835 nm. In some embodiments,it includes light wavelength(s) at which one or more other fluorescentdyes emit energy when excited. The invention is drawn to endoscopes andwands that can advantageously be used for visualizing and imaging in theinfrared spectrum, and preferably in both the infrared and visiblespectrums.

The term “endoscope”, as used herein, will be understood to encompasswands and laparoscopes, as well as endoscopes and other similar devices.

FIG. 2 illustrates a highly schematic view of an endoscopic system. Theendoscope 260 is placed in the proximity of a subject's tissue or insidea natural or surgically created opening in the subject.

An endoscope may have one or more illumination sources 220. Preferably,the illumination 220 source emits radiation having wavelengths in theinfrared spectrum, and images in the infrared spectrum. Infraredradiation at certain wavelengths can excite a fluorescent dye that hasbeen administered to the patient and cause the fluorescent dye to emitradiation. In certain embodiments, imaging may be performed in multiplediscrete bands of the spectrum. For example, imaging may occur in twodistinct infrared bands, in the infrared and visible spectrum, or in theinfrared and ultraviolet spectrum. In preferred embodiments, bothvisible and infrared light is emitted by one or more illuminationsources 220 for imaging in both the visible or infrared spectrums.

The one or more illumination sources 220 is in electrical communicationwith the computer 360. Through a computer interface, a user causes anillumination source(s) 220, such as an HPLD, to fire or otherwise emitradiation.

The illumination source 220 can be coupled to the existing fiber opticsin the endoscope or wand or coupled to an external cannula embedded withfiber optics or containing a working channel with sufficient diameter toplace a fiber optic or fiber optic probe for the transmission of anexcitation wavelength. The endoscope itself may contain a workingchannel sufficiently large for a laser fiber to be inserted and in thatcase a supplementary cannula or sheath for an excitation source wouldnot be required. Other suitable illumination sources are describedbelow.

In some embodiments, the illumination source 220 is in opticalcommunication with endoscope 260 by cable(s)/cannula(s) 280. If theillumination source 220 is a single emitter laser then it could becoupled to one cable 280. Alternately, a bar laser would requiremultiple fibers, which might be packed in the same or in multiplecables. Cable(s) 280 may connect to fibers integrated into the tubularportion of the endoscope 260 or to a sheath surrounding part or all ofthe endoscope 260. Fibers in the tubular portion or sheath then relaythe illumination to the patient's tissue.

Light from the illumination source(s) 220 is transmitted to thesubject's tissue. Reflected or emitted light from the subject's tissueis then transmitted to one or more detectors. These detector(s) are inelectrical communication with computer 360, which receives the imagescollected by the detector(s) and causes them to be displayed on adisplay 365. The computer 360 may further include software for imageprocessing.

I. Illumination Sources 220

The first step in imaging a dye (that is administered to a patient) thatemits in the infrared spectrum is to excite the dye. The dye may beexcited in the visible, ultraviolet or infrared spectrum. Preferably,the dye is a fluorescent dye. More preferably, the dye is atricarbocyanine dye. Most preferably, the dye is ICG. In someembodiments, multiple dyes may be used for imaging.

In one embodiment, the light source only emits light in the infraredspectrum. In some embodiments, light in both the visible and infraredspectrum is emitted. In some embodiments, the device of the invention,such as an endoscope or wand includes one or more LEDs that emits lightin the infrared spectrum and groups of 3 LEDs, producing red, green, orblue illumination, respectively, for visible imaging. In certainembodiments, the device includes LEDs producing or restricted toinfrared illumination combined with one or more white light LEDs. Lightsources may be bulbs or arc sources of metal halides, halogens and xenonthat emit in the blue, green and red and infra red wavelengths. LEDs andother light sources that emit in both the visible and infrared spectrumsare well known to the skilled artisan.

High power laser diodes (HPLDs) may also be used within the scope of theinvention. Examples of HPLDs include AlInGaAsP lasers and GaAs laserswhich are well known in the art. Such sources can be single diodes(single emitters), or diode-laser bars, which are made from edgeemitting semiconductor chips. Such sources can be operated in continuousmode (CW), quasi-CW, or pulsed mode.

These sources are capable of being remotely mounted in the system andcan be brought to the optical system used for viewing fluorescence viafiber coupling. This removes the HPLD, a powerful electrical device,from intimate contact with the patient, physician or technician.

The excitation wavelength, λ_(e), of ICG is 805 nm in whole blood. Therange of excitation wavelengths capable of exciting ICG ranges fromapproximately 710 nanometers to 840 nanometers, or more. This rangeoverlaps the fluorescence range of ICG whose peak, λ_(f), is 835nanometers. It is therefore necessary to use a narrow source such as anHPLD or similarly filtered Metal halide, Xenon, or Tungsten halogensources of radiation by means of an excitation or primary filter orfilters to excite the ICG.

HPLDs, made of AlInGaAsP/GaAs, have as their peak nominal output awavelength of 808 nm, with a tolerance of +/−3 nanometers. A drivingcircuit is necessary to provide power to the HPLD, the current andvoltage of which can be varied to lower the peak wavelength to 805 nm,the peak absorption of ICG.

Within the endoscope proper, an illumination pathway may take one of twoforms or a combination of the following: an integrated annulus of fiberoptic fibers encircling the optical elements for the transmission ofvisible light, and or an annulus of fiber optic fibers transmitting theenergy from an IR excitation source contained within a sheath or cannulainto which the imaging device is inserted.

II. Endoscopes and Wands

For example, endoscope 260 is shown in FIG. 3, and certain componentsare shown in FIG. 4. The endoscope 260 may include a distal section 3, arelay section 2, and a proximal section 29. Light travels from anillumination source 220 (not shown) to fiber cable 28 through the relaysection 2 and to the distal section 3. Reflected or emitted lighttravels from the distal section 3 having the objective assembly, throughthe relay section 2 and then through the proximal section 29 havingprisms to the detector(s) 33 (shown in FIGS. 9 and 10) in proximalsection 29. The detector(s) 33 detect the light and can form an image.The endoscope 260 may include an ocular and camera optics in theproximal section 29 to magnify or focus the image.

All the optical elements along the 3 segments of the longitudinal axisof the endoscope and wand are required to be coated for low reflectivityfor (preferably all) transmitting elements across all the wavelengths ofinterest, high reflectivity in all wavelengths of interest forreflecting surfaces contained within the distal section, and highseparation ratios in the proximal beam-splitting section. An embodimentfor a wand configuration contains in its distal portion both a deviatingand a beam-splitting prism assembly. Preferably each optical coating ona transmitting optical element is optimized for an angle of incidence oflight that is orthogonal or substantially orthogonal to each surfacealong a vector describing the opto-mechanical axis of the system withina range of plus or minus 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 degrees. Thisdoes not apply to the objective lens assembly where the departure fromnormal to the surface is greater.

The wand has the same components as shown in FIGS. 3 and 4, butgenerally has a different form factor since it is optimized for useoutside a person's body while an endoscope is optimized for insertioninto a person's body.

A. Distal Section 3

The distal section 3 of the inventive device may include an opticalassembly taking the form of an inverse telephoto with a distal negativepower lens group, a prism assembly 18 to deviate the line of sightwithin this deviating assembly and a positive lens group. A deviatingprism assembly 18 is contained between the distal lens groupcharacterized by its negative optical power and a proximal lens groupcharacterized by its positive power. This optical form (− +) is commonlycalled an inverse telephoto. Distal sections of endoscopes and otherdevices are well known in the art, and are described in, for example,U.S. Pat. No. 4,655,557 that is incorporated herein by reference in itsentirety.

Deviating prism assemblies 18 are routinely placed within the spacebetween the two powers of endoscopes used in visible wavelengths, asdescribed, for example, in U.S. Pat. No. 4,917,457, which isincorporated herein by reference in its entirety. Such deviating prismsallow the endoscope to be rotated around the shaft axis for a largereffective field of view. Examples of deviating prisms 18 are shown inFIG. 5. The angles shown are exemplary since a skilled artisan maydesign deviating prisms to facilitate the passage of the full beamdiameter or substantially the full beam diameter of the objective lensassembly through the prism with the following constraints, first thatthe ray path axis exiting the negative group of the objective lens becoincident or approximately coincident with the optical axis of theprism assembly group, second that the ray path enter the front face ofthe prism assembly perpendicular or approximately perpendicular to theface of the first surface of the prism assembly, thirdly, that the raypath exit the last surface of the deviating prism assembly perpendicularor approximately perpendicular or normal to the face of the last prismcomponent, and fourthly that the exit ray path optical axis becoincident or approximately coincident with the optical axis of thefollowing optical components.

The deviating prisms of the invention must displace or deviate the lineof sight. For example, the first prism (FIG. 5 (a)) has a zero percentdeviation, meaning that the wavelengths of interest are transmittedthrough each of the surfaces 19 a, 19 b, 19 c and 19 d.

In FIG. 5 (b), the line of sight is deviated thirty degrees. This meansthat the line of sight and coincident beam path is transmitted throughsurface 19 e, 19 f, 19 g, reflected by surface 19 h and 19 i, and thentransmitted through surfaces 19 j and 19 k.

FIG. 5( c) shows an example of a 45° deviating prisms. The line of sightand coincident beam path is transmitted through surfaces 19 l, 19 m and19 n, reflected by surfaces 19 o and 19 p, and then transmitted bysurfaces 19 q and 19 r.

A final example, FIG. 5 d, shows an exemplary 70° deviating prism. Theline of sight and coincident beam path is transmitted through surfaces19 s and 19 t, reflected by surfaces 19 u and 19 v, and then transmittedthrough surfaces 19 w and 19 x.

Thus, the reflective surfaces (e.g., 19 h, 19 i, 19 o, 19 p, 19 u and 19v) must be coated with a substance that reflects light in the infraredin preference to one that is optimized for the reflection of visibleonly. In preferred embodiments, in which the wavelengths of interest arein the emission range of ICG, the reflective surfaces are coated so thatthey reflect light between about 800 and about 850 nm, preferablybetween about 825 nm and about 835 nm. Most preferably, the reflectingsurfaces reflect both infrared and visible light. This high reflectanceof wavelengths in the infra red spectrum, and preferably in both thevisible and infra red spectrums, is achieved with a coating of gold,silver or aluminum. Gold is particularly preferred for reflecting onlywavelengths in the near infra red spectrum. Silver is particularlypreferred for reflecting wavelengths in the visible and near infra redspectrums. These coatings can be applied directly to the reflectingprism surface and are between about 1 and about 20 micrometers inthickness, and preferably between about 1 and about 10 micrometers inthickness. They can be purchased from, for example, TYDEX J.S.Co. (St.Petersburg, Russia) and vapor deposited onto the surface of interest byany number of thin film coaters in the world using vacuum depositionchambers. Gold coatings are especially preferred because they are knownto reflect well in the near IR and withstand autoclaving processes. Insome embodiments, any coating that reflects at least 80%, preferably atleast 90% and most preferably at least 95% of light energy that iswithin the wavelengths of interest may be used. A second coating, suchsilicon dioxide (SiO₂), magnesium fluoride, silicon monoxide or adielectric overcoat may be applied. Such coatings can be purchased from,for example, OFR, Inc., Caldwell , N.J.

The transmitting prism surfaces (e.g., 19 a, 19 b, 19 c, 19 d, 19 e, 19f, 19 j, 19 k, 29 l, 19 m, 19 q, 19 r, 19 s, 19 t, 19 w and 19 x eachtransmit wavelengths of light in the infrared and the visible spectrums.Any surface that is glued and not air-glass does not need ananti-reflecting coating applied.

B. Transmitting Members

The vast majority of optical surfaces that are used for transmitting thewavelengths of interest (“transmitting members”) are in the relaysection. The discussion of transmission coatings, below, is framed inreference to transmitting members in the relay section, though it isequally applicable to transmitting members in other parts of theendoscope or wand.

The positive lens group in the objective lens assembly forms a realimage from the energy received from outside the device for relay to therelay section 2. The relay section 2 includes multiple relay optics (notshown) that relay the image by producing a series of intermediate imagesto the proximal section 29. The proximal section 29 will be furtherdescribed below.

The prior art optical coatings on devices such as endoscopes and wandshaving relay optics are optimized for the visible spectrum and arebiased towards the blue as shown in the representative scans of suchcoatings on optical glasses, such as F2 and SF6 in FIG. 6. However, suchprior art coatings reflect more than 5% of the infrared energy at eachglass/air surface. Since a typical relay section 2 could have a largenumber (e.g., 30-40) glass/air surfaces, the resulting reflectance makesthe devices unusable for infrared imaging.

Devices of the invention must have coatings in the relay and othersections that transmit wavelengths in the infrared spectrum that are ofinterest. Preferably, the coatings have a reflectance of the wavelengthsof interest that are no more than about 0.5%, no more than about 0.4%,no more than about 0.3%, no more than about 0.2% and most preferably nomore than about 0.5%. In some embodiments, coated relay optics eachreflect between about 0.5% and about 5% of the wavelengths of interest,and preferably between about 0.5% and about 3%.

The wavelengths of interest will depend on the application. For example,if ICG is injected into and excited in a human being, the wavelengths ofinterest will include the wavelengths at which ICG emits energy. In suchan application, the wavelengths of interest might be 825-830 nm. In apreferred embodiment, the coating is optimized to minimize reflectanceboth in the infrared and visible spectrums, thus allowing viewing inboth the infrared and visible spectrums. The visible spectrum iscommonly considered to be between about 400 nm and about 700 nm.

The coating preferably includes alternating layers or pairs of layers.These pairs include a high and a low index coating material thattogether make up a pair. Suitable pairs include TiO₂ and MgF₂, TiO₂ andSiO₂, Zirconium Oxide (ZrO₂) and MgF₂, and tantulum pentoxide (Ta₂O₅)and SiO₂. The number of repeating pairs that may be used is betweenabout 2 and about 100, preferably between about 2 and about 50, betweenabout 2 and about 40, between about 2 and about 30, and between about 2and about 20 for any optical surface. In some embodiments, the coatinghas a minimum of 6, 7, or 8 pairs. In certain embodiments, the coatinghas a minimum of 4 pairs. In some embodiments, the coating has a minimumof 10 pairs. A coating may have one or more different pairs. A usefullow index material is SiO₂ with an index of refraction of approximately1.45 in the visible. SiO₂ would be paired with a high index materialsuch as Ta₂O₅, which has an index of 2.4 in the visible, in slightlydifferent ratio when placed on a low index of refraction glass, such asBK7, than on a high index glass, such as N-SF57. In some embodiments, ahigh refractive index material is one having an index of refraction fromabout 1.9 to about 2.4 in the visible spectrum as measured at 633 nm. Alow refractive index, in some embodiments, is one having an index ofrefraction from about 1.45 to about 1.8 as measured at 633 nm.

FIG. 7 illustrates an example of one such coating that is optimized tohave low reflectance around the emission range of ICG. It is comprisedof alternating layers of MgF₂ and TiO₂.

FIG. 8 illustrates another example of a low reflectance coating suitablefor use in the relay optics of the invention. This coating hasalternating layers of SiO₂ and TiO₂, and one pair of MgF₂ and TiO₂.

In choosing glasses or optical surfaces, the skilled artisan considers anumber of factors to favorably correct the optical aberrations and coverthe desired field of view on the detector chosen with a minimum ofuncorrected residual aberrations. In choosing the glass type, factors toconsider are measure of bending power, index, a measure for theirdispersing power, and geometric variables such as radius of curvature,thickness of glass and thickness of air, the order of glasses throughthe system and other factors well within the ability of the skilledartisan. Glasses used in the relay sections of the devices of theinvention could, for example, cover a range of about 1.5 to about 2.0 asa measured by their index of refraction. While there are many air-glasssurfaces in a device of the invention, not every one will represent adistinct coating choice. There may be groupings of glasses with similarindices that will be coated in the same vacuum deposition chamber run.For example, a grouping might be made of glasses with an index range of1.5 to 1.65, 1.65 to 1.7, and so forth. The judgment will be made basedon performance of the whole stack of pairs used for the particularcoating design. The criteria for the design goals will includewavelengths and or range of interest chosen and their relative weighingat measurable points, angles of incidence chosen and their relativeweighing, environmental considerations, and cost.

The thin film designer, in designing a coating suitable for one or morerelay glasses, considers, for example, pairs of high and low indexmaterial, their individual thickness (in optical terms, i.e. they arewavelength dependent because they have an index of refraction), theirpair thickness, and the substrate glass index. Antireflective coatingsand dielectric mirrors are discussed in the publication ElectromagneticWaves and Antennas, published by Sophocles J. Orfanidis on the website<http://www.ece.rutgers.edu/˜orfanidi/ewa> which are attached at the endof this specification.

In some embodiments, devices such as a “chip-on-a-stick” do not userelay optics, but rather pass light energy from the distal section 3 tothe proximal section 29 through fiber optics. In such embodiments, theskilled artisan will understand that there are no relay optics to becoated. Chip-on-a-stick designs eliminate the proximal position of thedetector and move said detector plane to the image plane of theobjective lens assembly. The preferred inventive chip-on-a-stick designonly images in the infra red spectrum though those that image in boththe infra red and visible spectrum are within the scope of theinvention.

C. Summary of Dichroic Filter and Cameras

Referring to FIGS. 3, 4, 5, 9, 10, and 11, the beam splitting proximalprisms/dichroic filters 31 receive light from relay section 2 or theexit pupil of a distal section 3 and focuses light onto the detectors33. In some embodiments, the relayed image only includes light in theinfra red spectrum. This image is directed to detector 33 b which may bea single charge coupled device (CCD) or complementary metal-oxidesemiconductor (CMOS) or any other type of detector that can detectinfrared light. While infrared blocking filters are commonly used toblock out infrared light in endoscopes that do not obtain infraredimages, the skilled artisan will understand that such filters should notbe used in this embodiment.

In certain embodiments, the device is configured to visualize both inthe infrared and visible spectrum. Thus, the light energy received fromthe distal and relay sections is in both the visible and infraredspectrum. In this embodiment, the proximal prisms 31 separate thewavelengths and relay them to detectors capable of detecting appropriatewavelengths.

The proximal prisms 31 must have substantially equal path lengths toeach detector 33 to yield similar magnifications for such comparisons orsuperimposed imaging. These proximal prisms 31 could take many forms,but they share approximately equal path lengths per detector and the useof dichroic filters that substantially enhance the optical efficiency orthroughput of the system when compared with metalized beam splittercoatings.

Preferably, the ratio of the unfolded optical path length to diameterratio in each light pathway through the proximal prism assembly is givenby:

1.75W<L<3W

-   -   where    -   W is the diagonal of the exit face of the unfolded path of any        or all of the prisms    -   L is the path length along the optical axis and corresponds to        the focal length of the focusing optics minus an air space on        either side of L

As described above, ICG has a peak excitation wavelength at 805 nm. Therange of excitation wavelengths capable of exciting ICG ranges fromapproximately 710 nanometers to 840 nanometers, or more. This rangeoverlaps the fluorescence range of ICG whose peak, λ_(f), is 835nanometers. The challenge is that the fluorescent return signal, in thenear infrared (NIR) for example, can be significantly lower than that ofthe visible channels which are transmitting a scattered return. Thisdifferential between low fluorescent return and normal visible returnrequires not only highly efficient coatings not found on normalendoscopes and wands but also improvements associated with the detectorassembly. An optical design optimized for the visible is slightlydifferent than that of an optical design for visible (VIS) plus NIRimaging. However, a comparable design can be used for both regions, ifthe back focus is allowed to vary in length along the z or optical axis.A NIR image is formed behind that of a visible wavelength of either Red,Green or Blue because NIR wavelengths are longer; hence we want to varythe back focus of the NIR image found exiting the face of the proximalprism assembly.

In certain embodiments, the proximal prism assembly 31 is organized bywavelength in a short to long or long to short order by means ofdichroic beam-splitting coatings contained within the prism assembly.For example, in the case of a 4 channel prisms associated with threedetectors that detect in the visible range, and one detector thatdetects in the infrared range, λ1<λ2<λ3<λ4. Thus, λ1, λ2, and λ3 areassociated with 400 nm to 700 nm and λ4 is dedicated to 810 nm to 870nm, approximately for the long pass configuration.

An imaging pathway will require a barrier or secondary filter requiredto block the excitation radiation from reaching the detectors. Thisbarrier filter is a dichroic filter made up of high and low indexmaterials evaporated onto a substrate whose arrangement disposes thefilter to have a lower and upper cutoff encompassing a range ofwavelengths above that of the excitation wavelength, λ_(e), whose peakis 805 nm for ICG. The skilled artisan will understand that other dyeswill have other λ_(e) and will hence require different filters forimaging. Wavelength ranges below the cutoff frequency must be blocked toan optical density of 5 or more so that the detector does not view anyportion of the energy from the illumination source, as it may be 2 ormore orders of magnitude more intense than the fluorescent response. Thedichroic filter may be positioned as a plane parallel plate orthogonalto the optical axis or at some preferential angle to minimize ghostimages.

To maximize the lens coupling efficiency to the detector it is importantto design the focusing optics and beamsplitting prism assembly toproduce a marginal ray angle in the corner of the field which departsfrom the opto-mechanical axis by 10 or 15 degrees or less from the lastoptical element in the focusing optics to the detector. It is in thispath that the prism assembly 31 is placed. By possessing a shallowmarginal ray angle, the ray paths from the various fields within theprism reflect or pass the dichroic filters 31 at a nearly common angleor over a small range of angles. The more similar these angles, thebetter optical efficiency or throughput for each wavelength range, asdichroic filters by their nature are angle sensitive. Preferably, theseangles do not differ from each other by more than 10, 9, 8, 7, 6, 5, 4,3, 2, or 1 degrees.

Moreover, due to the low signal strength in the NIR path of the weakfluorescent scenes the f-number of the combined NIR VIS focusing andbeamsplitting assembly should be as fast as possible for increasedsensitivity. The increased sensitivity yields a larger cone angle fromthe last focusing element through the beamsplitting assembly creating alarger angle range than would be required for VIS imaging alone.Likewise, it is important to make each channel's ray path similar inlength so that the resulting image height, magnification, on alldetectors is comparable.

In the case of exceptionally weak NIR fluorescent signals, a cooled orintensified detector may be used on the NIR path. The improvedsensitivity may be provided by an intensified CCD (ICCD) or electronmultiplying CCD (EMCCD). Similarly, an intensifier or cooler means maybe integrated to the infrared detector or beamsplitting assemblyassociated with the detector to make an integrated and compact system. Abarrier filter may be used adjacent to an infrared detector to removewavelengths outside those of interest.

In certain embodiments, a total of two detectors 33 are used (see e.g.,the top prism 31 in FIG. 4 and FIG. 9). One detector 33 a detects lightin the visible spectrum and the second detector 33 b detects light inthe infrared spectrum. Proximal prism assembly 31 includes a firstchannel 31 a and a second channel 31 b.

Light from the relay section 2 enters channel 31 a through surface 34 a.Visible light is transmitted through surface 34 b and 34 c to apolychromatic detector 33 a. The polychromatic detector 33 a may be asingle CCD or CMOS detector with an integrated color filter, such as aBayer pattern directly on the detector.

Infrared light from relay section 2 is reflected by surface 34 b and 34c onto surface 34 d, through which it is transmitted to infrareddetector 33 b. Acceptable infrared detectors for any embodimentsdescribed herein include silicon. Silicon is the base material of almostall detectors commonly used, and it has a peak efficiency in the nearinfra red spectrum.

In certain embodiments (FIGS. 4 and 10), a 4 channel prism assembly 31is used. Prism assembly 31 includes a channel for each of red, green,blue, and infrared, and is coupled to a detector capable of detectingsuch light. In the case of the 4 channel prism the 4^(th) detector isinto the page and not seen.

Thus, in certain embodiments, multiple detectors are present in anendoscope of the invention. Preferably, the diagonal of the infrareddetector or intensifier associated with the infrared detector isapproximately the same length as the diagonal of one or more of theother detectors that image in another spectrum.

Acceptable dichroic coatings which may be used within the context of the2 and 4 channel prisms (31) may be purchased from Feldmann Optics inWetzlar Germany, for example. Prism surfaces designed to transmit thewavelengths of interest are preferably coated as described in thetransmitting members section, above.

The detectors 33 a and 33 b are synchronized and the frame grabber sendssignals from all detectors to a computer. The sent data is input invideo RAM. The user can access one or both of the visible and/orinfrared images. Preferably, the computer includes computer program codethat, when executed, gives the user the choice to either see (a) thevisible image, (b) the infra red image, (c) both simultaneously (i.e.,one superimposed over the other) with controls to dim the visible image,for example, so there is some color information in the displayed image,(d) alternating display of visible and infra red images, and/or (e) sideby side viewing in different windows. Preferably, when both infra redand visible images are obtained, the two sets of images are viewed withperfect or substantially perfect registration.

In certain embodiments, field sequential illumination technology, suchas described in U.S. Pat. No. 6,960,165, U.S. Pat. No. 6,388,702, andU.S. Pat. No. 6,907,527 may be used These patents are incorporatedherein by reference in their entirety.

A number of functionalities are made possible because detectors 33detect one or both of infrared and visible light. For example, inembodiments where multiple detectors 33 are used (e.g., an infrared anda visible light detector), the detectors may have an automatic gainfunction. For example, the two detectors may send information to thecomputer 360 indicating the amount of energy detected by each. Thecomputer 360 may have computer code for adjusting the gain of eachcamera based on this information. In some embodiments, the user mayadjust the gain of the detectors through a computer interface.

CMOS sensors allow gain manipulation of individual photodiodes,region-of-interest read-out, high speed sampling, electronic shutteringand exposure control. They have a large dynamic range as well as aformat for the computer interface. The skilled artisan will understandthat the gain of individual pixels may be asynchronously modified inCMOS detectors. For example, areas for which greater performance isrequired may be made more sensitive. Similarly, in certain areas,response from the detectors may be decreased to, for example, counteractblooming. Such fine-tuning may be effected by the user or automaticallyas described above.

In certain embodiments, the detectors may be used to regulate the amountof illumination emitted by the illumination source(s) 220. This isparticularly important as infrared energy may be harmful to humans, andwhile the photo bleaching properties of dyes such as ICG provide anupper limit on the energy applied to the tissue and require low dosagesof wavelengths not unlike red in amounts of approximately 50 milliwattsper cm squared. Nonetheless, the perception of NIR as wavelengths whichproduce a substantial amount of heat is well founded. For example,detectors 33 b and 33 a automatically sense exposure levels of infra redenergy and visible energy, respectively, and electronically communicatethis information to the computer 360. Software on the computer may thencompare the energy level indications received from the differentdetectors 33 a and 33 b. If the software determines that the level ofinfrared energy exceeds the level of visible light energy, the softwaremay instruct the computer 360 to decrease the output of the infraredillumination source. In certain embodiments, the software may have apre-set threshold or may allow a user to set a threshold as to anacceptable difference in energy output between different power sources.If a determination is made that the infrared detected energy exceeds thedetected visible light energy by the threshold amount, the computer willthen instruct the illumination source 220 to decrease output.

In some embodiment, if the software on the computer 360 determines thatno infrared energy is being detected by the infrared detector, it mayinstruct the infrared camera to cease transmitting information to thecomputer or no longer use information transmitted from the infrareddetector in calculations and imaging.

In some embodiments, proximal section 29 comprises an ocular member withan exit window. Such a window is useful to a physician who wishes tolook through the endoscope without a camera. Proximal prisms will beprovided to relay a visible image to the window, or the visible/infrared proximal prism camera invention may be used.

In certain embodiments, the physician may not wish to image in theinfrared spectrum. In such embodiments, the infrared camera may beturned off, powered down or removed from the endoscope. In preferredembodiments, such turning off, powering down or removal will activatesensors or be otherwise detected by the computer, which will then send ashut off command to the infrared illumination source.

Preferably, where the aspect ratio of the prism contained within thefocused beam path to the detector is defined by the exit face to theprism, the face in near proximity to the detector, and its length, asdefined by the path along the optical axis, -yields:

0.167<D/L<0.25

-   -   where:    -   D is defined by the diameter of the exit face, and    -   L is the path along the optical axis contained within the prism

In certain embodiments, the proximal prism assembly is removable fromthe endoscope eyepiece or last optical relay member, thus requiring afocusing lens assembly that focuses the relayed light from the relaysection of endoscope 260 to an external exit pupil. This focusing lensassembly is preferably color corrected to produce comparably sizedimages free of dominating aberrations in each of the desired color bandsand corrected to compensate for the positioning of the compact proximalcolor splitting prism assembly. The focusing assembly must betelecentric in object space, that space between the endoscope relay andthe detachable compact prism assembly first optical element. In the caseof a proximal prism assembly detachable from an endoscope eyepiece thefocusing lens assembly must have an external entrance pupil that maps oris positioned in close proximity to the exit pupil of the endoscopeeyepiece.

In the later case an endoscope exit pupil cannot be designed much largerthan the human eye pupil that views it. The mismatch between human eyepupil and endoscope exit pupil would be seen as a reduction inbrightness by the user of the endoscope when used without a camera,whereas the larger the pupil the faster the f-number of the focusinglens assembly and more sensitive the system from the camera ordetector's point of view.

III. Light Sources

The invention further provides a non-laser infra-red light source thatcan be used with endoscopes, wands, macro telephoto imagers, or anyother imaging device that is capable of receiving an optical fiber.Thus, the dangers associated with lasers, such as damage to a user's orsubject's retina are removed or minimized. In some embodiments, thenon-laser source is part of a combined illumination source comprised ofboth VIS and NIR illumination. In certain other embodiments, thenon-laser source is contained in a distinct housing (e.g., a light box)in optical communication with the imaging device through fiber optics.

Referring now to FIG. 11, the light source includes light emittingmember. Light emitting member is any light emitter that emits lightenergy in the infra red spectrum. Examples include tungsten halogen,xenon, and metal halide bulbs or arcs. In some embodiments, a memberthat emits in multiple wavelength ranges (e.g, infra red and visible) ischosen.

The light source includes an integrated reflector. Preferably, thereflector captures a significant portion of the total source power ofthe bulb or arc. An elliptical reflector captures a significant portionof the solid angle of the source when the reflector is positioned at oneof the two foci of the ellipse, where the reflector can then redirectenergy from the source arc or filament to the second foci defined by theelliptical reflector. In other embodiments, the reflector is parabolic.

The reflector has a coating that reflects infra red light to thebeamsplitter that separates light of different wavelength. Infra redlight from beamsplitter is then focused onto light fiber by opticalassembly. The light fiber for NIR has a diameter and acceptance angle tofavorably capture a substantial portion of the infra red light.Preferably, the beamsplitter routes light in the range of about 750 nmand about 800 nm to the optical assembly. In one embodiment, thenumerical aperature is between about 0.4 and about 0.66. In someembodiments, the numerical aperture is between about 0.55 and about 0.66NA. Such a combined VIS and NIR source can be used to provideillumination for endoscopes, wands, and macrotelephoto imaging devicesused for NIR fluorescent imaging or combined VIS and NIR fluorescentimaging in either mono or stereo viewing mode.

In cases where the reflector is elliptical, the light member will bepositioned approximately at the first foci of the ellipse, and the lightfiber will be positioned approximately at the second foci which may bereimaged by a condenser lens assembly with a collimated or nearlycollimated section between the said condenser lenses. Preferably, anassembly of collimating and focusing lenses is positioned between themember and the light beam splitter to collimate the light directed tobeamsplitter 320. The advantage of the above configuration is thecreation of near parallel paths of rays, the collimated condition, whenintersecting a dichroic coating. The cut on cut off slope of such acoating is steeper if all rays are more or less parallel wheninteracting with the coating, therefore making it more efficient atdividing a spectrum.

In certain embodiments, the integrated reflector is parabolic. In theseembodiments, the reflected light will be approximately collimated, and acollimating assembly may not be necessary to collimate the reflectedlight. A focusing lens or lens assembly is required to focus the energyfrom the source to the fiber optic cable.

Reflectors of other shapes may be used. Examples include: a reflectorwhose shape is modified to compensate for the aberrations of the glassenvelope surrounding an arc source.

As discussed above, reflector has a coating for preferentiallyreflecting light in the infra red spectrum. Preferably, light atwavelengths between about 750 nm- about 820 nm is reflected. In certainembodiments, light between about 750 nm and about 800 nm is reflected.In some embodiments, light having a wavelength of between about 770 and800 nm is reflected. In some embodiments, a coating is chosen thatreflects significant amounts of light in multiple spectrums (e.g.,ultraviolet, visible and/or infrared) and/or within multiple rangeswithin one or more of these spectrums.

In some embodiments, the coating is one of gold, silver or aluminum.Gold is particularly preferred for reflecting only wavelengths in thenear infra red spectrum. Silver is particularly preferred for reflectingwavelengths in the visible and near infra red spectrums. These coatingscan be preferably applied directly to the reflecting reflector 310 andare between about 1 and about 20 micrometers in thickness, andpreferably between about 1 and about 10 micrometers in thickness. Theycan be purchased from, for example, TYDEX J.S.Co. (St. Petersburg,Russia) and vapor deposited onto the surface of interest by any numberof thin film coaters in the world using vacuum deposition chambers. Goldcoatings are especially preferred because they reflect well in the nearIR. In some embodiments, any coating that reflects at least 80%,preferably at least 90% and most preferably at least 95% of light energythat is within the wavelengths of interest may be used. A secondcoating, such silicon dioxide (SiO₂), magnesium fluoride, siliconmonoxide or a dielectric overcoat may be applied. Such coatings can bepurchased from, for example, OFR, Inc., Caldwell, N.J. In someembodiments, the coating is a dichroic coating or mirror (provided by acoating supplier such as Omega Optical Inc. Brattleboro, Vt. or ChromaTechnology Corp., Rockingham, Vt.) A coating of gold, silver or aluminumis preferred over dichoroic coatings for efficiency since they are anglesensitive and such coatings could, over the collecting surface of thereflector, vary in efficiency.

Referring now to the beamsplitter, it routes energy in the infra redspectrum to light fiber. The light energy routed to light fiber iswithin the spectrum desired for imaging. In other words, if the dyebeing used is ICG, the beamsplitter will direct light to the light guidethat is capable of exciting the ICG. For example, it may have awavelength between about 750- about 820 nm, and more preferably betweenabout 750 nm and 800 nm, or between about 770 nm and about 800 nm. Thebeam splitter may be an optical plate coated with, or cube containing adichroic coating or interference filter such as a high/low index paircoating described above in relation to the endoscope relay section. Theconfiguration of such an interference filter varies from transmissionfilters in selection and placement of high/low index pairs to optimizeblockage and spectral width. In some embodiments, the beamsplitterassembly may require an absorptive filter that absorbs light rays thatare at a wavelength above or below the wavelengths of interest. If theenergy is sufficiently intense there may be excess heating that can beameliorated with the addition of a fan.

FIG. 12 shows another embodiment of the light source. It is similar tothe previously described light source except that the light memberincludes a second optical fiber that provides light at differentwavelengths than the first optical fiber. Thus, it can be used formultimodal imaging (e.g., simultaneous imaging in the infra red spectrumand also imaging in the visible spectrum). In this embodiment, lightemitting member is chosen such that it produces light both in the infrared and in the second desired range. Preferably, the second range iswithin the visible spectrum of about 400 nm to about 700 nm. Reflectorincludes a coating that reflects light in both the infra red and in thesecond desired range, e. g., silver. The beam splitter than routes lightwithin the second desired range to second light fiber.

In some embodiments, additional absorptive filters may be placed betweenbeamsplitter and one or more of the first and second light fibers tofurther reduce unwanted energy. Locating these filters in this positionhas several advantages. The first is; there is physically more room thanthe earlier case where the absorbing filters were located between thefirst and second foci of the elliptical reflector. The second advantageis also associated with more space, as the beam diameter may be largerthan in the converging beam path between the two foci. This results inless flux density on the filter and less substrate heating in thefilter. Thirdly, more room results in freedom to use more filters ofdiffering configurations. Fourthly, more room permits the use of thickermore efficient absorptive filters.

In certain embodiments, the alpha angle of the light emitting member,the reflector and focusing lens in a one-dimensional direction satisfythe condition of 0.42 for the ratio of D/L<tan alpha<1.4 D/L where alphais the angle of the marginal ray and where D is one half of theeffective diameter of the reflector adjacent to the light emittingmember 300 or focusing lens to insert energy from light emitting member300 to the light fiber and L is the distance from the limiting apertureof either the reflector or focusing lens.

Many modifications and variations of this invention can be made withoutdeparting from its spirit and scope, as will be apparent to thoseskilled in the art. The specific embodiments described herein areoffered by way of example only and are not meant to be limiting in anyway. It is intended that the specification and examples be considered asexemplary only, with a true scope and spirit of the invention beingindicated by the following claims.

1. An endoscope or wand device comprising light transmitting members,said light transmitting members comprising an optical coating thattransmits between about 95% and about 99.5% of light energy at awavelength within the infra red spectrum.
 2. The device of claim 1,further comprising a deviating prism assembly having at least onesurface coated with gold, silver or aluminum.
 3. The device of claim 1,wherein the coating on the transmitting members comprises alternatinglayers of dissimilar optically transparent dielectric materials.
 4. Thedevice of claim 3, wherein the dielectric materials are selected fromthe group consisting of titanium dioxide (TiO₂), silicon dioxide (SiO₂),zirconium oxide (ZrO₂), magnesium fluoride (MgF₂) and tantulum pentoxide(Ta₂O₅).
 5. (canceled)
 6. (canceled)
 7. The device of claim 1, whereinthe coating on the transmitting members comprises between about 2 andabout 40 pairs of alternating layers of dissimilar optically transparentdielectric materials. 8-10. (canceled)
 11. The device of claim 1,wherein the wavelength within the infra red spectrum is a wavelength atwhich an excited fluorescent dye emits energy.
 12. The device of claim11, wherein the fluorescent dye is ICG.
 13. The device of claim 11,wherein the wavelength within the infra red spectrum is between about825 nm and about 835 nm. 14-21. (canceled)
 22. A near infra-red lightsource comprising: a light emitter that emits light in the infra redspectrum; a reflector comprising a first coating that routes light inthe infra red spectrum toward a beam splitter that transmits light inthe infra red spectrum; said beam splitter comprising a second coatingfor routing light in the infra red spectrum toward a light guide havinga numerical aperture between about 0.4 and about 0.66.
 23. (Canceled)24. The light source of claim 22, wherein the reflector is elliptical.25. The light source of claim 22, wherein the reflector is parabolic.26. The light source of claim 22, further comprising a collimating lensassembly positioned between the beam splitter and the reflector.
 27. Thelight source of claim 22, wherein the first coating comprises a metalselected from the group consisting of gold, silver and aluminum. 28.(canceled)
 29. (canceled)
 30. The light source of claim 22, wherein thebeam splitter routes light having a wavelength between about 750-800 nmto the light guide.
 31. The light source of claim 22, wherein the beamsplitter further routes light in the visible spectrum to a second lightguide.
 32. The light source of claim 22, wherein the second coatingincludes alternating pairs of high and low index materials.